Technological advances have provided a unique opportunity to examine the contribution of the period before birth to subsequent human health and development. Interest in fetal origins of childhood and adult well-being has increased exponentially in recent years. We have been documenting normative development of the fetus for the past 15 years under the auspices of this award. Our goals have, and continue to be, threefold. These include: characterizing normal patterns of development of fetal neurobehavioral and physiological functioning during gestation in healthy, low risk pregnancies (Ontogeny); determining how maternal mediators, both psychological and physiological, affect the course of antenatal development (Maternal Influences); and evaluating continuity in function from prenatal to postnatal development in order to understand the origins of individual differences (Prediction). The next project period will focus on our evolving interest in the gestational roots of the earliest relationship, generated by the emergent recognition of the intrinsically dyadic nature of gestation. Two studies are proposed. In the first, responses of 155 maternal-fetal pairs to elicitors of behavioral and physiological reactivity will be evaluated at four gestational periods (i.e., 18, 24, 30, and 36 weeks) to clarify the relative contribution of mothers and fetuses in influencing the intrauterine milieu and to evaluate how these processes change over gestation. This study will also examine maternal psychological adaptation to pregnancy within the context of maternal-fetal synchrony. The second study will evaluate the manner in which maternal-fetal interaction and synchrony contributes to maternal-child interaction and synchrony during the third year life by following 120 pairs who participated in an antenatal longitudinal study. Prenatal data included maternal-fetal biobehavioral monitoring during five serial visits at three week intervals, commencing at 24 weeks gestation. When offspring are 2-1/2 years old, toddlers and mothers will participate in a laboratory-based procedure designed to measure the degree of behavioral and physiological synchrony of the pair under conditions of baseline and challenge. Taken together, these studies will further our understanding of the antenatal factors that impinge, positively or negatively, on the developing fetus and pregnant woman and provide the foundation of the earliest relationship.